The present invention generally relates to a semiconductor layer structure having an aluminum-silicon alloy layer, and in particular to a semiconductor layer structure having an aluminum-silicon alloy layer which makes contact with a semiconductor substrate, so that the Schottky barrier contact or ohmic contact can be formed therebetween.
A conventional Schottky barrier diode has a layer structure which contains an n-type silicon (Si) substrate, a silicon dioxide layer (SiO.sub.2) having a contact hole, and a metallic electrode formed in the contact hole and on top of the silicon dioxide layer. An interface between the metallic electrode and the silicon substrate forms a Schottky barrier. The metallic electrode contains aluminum (Al), platinum (Pt), tungsten (W), gold (Au) or the like. For example, the metallic electrode may be formed by a pure Al layer. Alternatively, an Al-Si alloy layer may also be used for forming the metallic electrode. The use of an Al-Si alloy layer has been proposed in the Japanese Laid-Open Patent Application Nos. 17563/1984, 124765/1984 and 20568/1985, for example.
The Application No. 175763/1984 discloses an Al-Si alloy layer (first layer) which makes contact with a Si substrate. A barrier layer (second layer) made of titanium nitride (TiN) is formed on the Al-Si alloy, and an interconnection (wiring) layer (third layer) constructed by an Al-Si alloy layer is formed on the barrier layer. The above publication shows that in the case where the first and third layers are constructed by an Al alloy, the Al alloy may have a composition which is the same as a composition of an Al alloy which is generally used as a wiring substance. Normally, an Al-Si alloy used for forming a wiring layer contains Si of up to 2 weight percent (wt. %). The Application No. 20568/1985 also discloses an Al-Si alloy which is used for constructing the Schottky barrier diode and which has the Si concentration of a few percent by weight. That is, using an Al-Si alloy film in which Si of a few percent by weight is contained is the common practice by those skilled in the art.
In general, a rise voltage of the Schottky barrier diode depends on the Schottky barrier height. The rise voltage increases with an increase of the Schottky barrier height. In the case where the Schottky barrier diode is used in a bipolar type static random access memory or a transistor-transistor logic (TTL) circuit, the Schottky barrier diode is required to have a high Schottky barrier height so as to result in a high rise voltage. However, with the Al-Si alloy having the Si concentration of a few percent by weight, it is very difficult to obtain a sufficiently high Schottky barrier height. According to the Application No. 124765/84, in the case where an Al-Si alloy is formed directly on the Si substrate, the Schottky barrier height obtained is equal to 0.65 [eV], although the Si concentration thereof is not shown in the publication. The above value of the Schottky barrier height cannot provide for the rise voltage which satisfies the above requirement well. That is, a Schottky barrier height greater than the above value is desired.
It is known to change layout of a pattern on the substrate to thus obtain a high Schottky barrier height. However, change of layout considerably decreases the degree of freedom of design of LSI devices.
It is conceivable to obtain an increased Schottky barrier height by reducing a contact area of the Al-Si alloy layer on the Si substrate. However, there is a limit on reduction in size of the contact area with the current LSI production techniques. Therefore, the above is not a useful measure.